1. Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé 404, 2800 Kgs. Lyngby, Denmark
2. Institute of Dynamics and Vibration Research, Leibniz Universität Hannover, Appelstr. 11, 30167 Hannover, Germany
3. Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824
4. Institute of Applied Mechanics, Technische Universität München, Boltzmannstr. 15, 85748 Garching, Germany
5. Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
6. Department of Mechanical Engineering, William Marsh Rice University, 6100 Main St., Houston, TX 77005